Abstract: A method for starting a fuel cell in a fuel cell system, at temperatures below the freezing point of water, includes, in a first step, that the hydrogen concentration in the anode is increased; after which, in a second step, an anode pressure is increased for a fixed period of time, and while air is supplied to the cathode, the maximum possible current is drawn from the fuel cell, and after which, in a third step, the fuel cell is switched in a load-free manner and the anode pressure is reduced. After the third step, the second step and the third step are repeated successively until a sufficient performance of the fuel cell for its normal operation is reached.

Abstract: Methods are disclosed for detecting and lessening fuel starvation conditions in an operating fuel cell system. The fuel cell systems comprise a solid polymer electrolyte fuel cell with a regulating apparatus for regulating the pressure of fuel supplied to the anode inlet of the fuel cell, in which the outlet pressure from the regulating apparatus oscillates during operation. The methods involve monitoring an electrical output of the fuel cell during operation, determining the amplitude of oscillation in the electrical output, and then, if the determined amplitude of oscillation in the electrical output exceeds a predetermined amount thereby indicating a fuel starvation condition, taking a remedial action to lessen the fuel starvation condition.

Abstract: A method for starting a fuel cell in a fuel cell system, at temperatures below the freezing point of water, includes, in a first step, that the hydrogen concentration in the anode is increased; after which, in a second step, an anode pressure is increased for a fixed period of time, and while air is supplied to the cathode, the maximum possible current is drawn from the fuel cell, and after which, in a third step, the fuel cell is switched in a load-free manner and the anode pressure is reduced. After the third step, the second step and the third step are repeated successively until a sufficient performance of the fuel cell for its normal operation is reached.

Abstract: Methods are disclosed for starting up a fuel cell system from starting temperatures below 0° C. The methods apply to systems comprising a solid polymer electrolyte fuel cell stack whose cathodes comprise an oxygen reduction reaction (ORR) catalyst and whose anodes comprise both a hydrogen oxidation reaction (HOR) catalyst and an oxidation evolution reaction (OER) catalyst. In the methods, from the beginning of starting up until the fuel cell temperature reaches 0° C., the fuel cell stack current is kept sufficiently low such that the current density drawn does not exceed the stack's capability for the oxidation evolution and the oxygen reduction reactions to occur at the anode and cathode respectively (i.e. current density drawn is less than the stack's maximum OER/ORR current density).

Abstract: Improved methods are disclosed for shutting down and storing a fuel cell system, particularly for below freezing temperature conditions. The methods comprise stopping power production from the fuel cell stack, monitoring its temperature, and repeatedly performing a predetermined warming operation if the stack temperature falls to a normal threshold temperature. In the improved methods, either an initial threshold temperature and/or an initial warming operation are used that differ from the respective normal threshold temperature and the predetermined warming operation.

Abstract: Methods are disclosed for detecting and lessening fuel starvation conditions in an operating fuel cell system. The fuel cell systems comprise a solid polymer electrolyte fuel cell with a regulating apparatus for regulating the pressure of fuel supplied to the anode inlet of the fuel cell, in which the outlet pressure from the regulating apparatus oscillates during operation. The methods involve monitoring an electrical output of the fuel cell during operation, determining the amplitude of oscillation in the electrical output, and then, if the determined amplitude of oscillation in the electrical output exceeds a predetermined amount thereby indicating a fuel starvation condition, taking a remedial action to lessen the fuel starvation condition.

Abstract: Methods are disclosed for starting up a fuel cell system from starting temperatures below 0° C. The methods apply to systems comprising a solid polymer electrolyte fuel cell stack whose cathodes comprise an oxygen reduction reaction (ORR) catalyst and whose anodes comprise both a hydrogen oxidation reaction (HOR) catalyst and an oxidation evolution reaction (OER) catalyst. In the methods, from the beginning of starting up until the fuel cell temperature reaches 0° C., the fuel cell stack current is kept sufficiently low such that the current density drawn does not exceed the stack's capability for the oxidation evolution and the oxygen reduction reactions to occur at the anode and cathode respectively (i.e. current density drawn is less than the stack's maximum OER/ORR current density).

Abstract: Improved methods are disclosed for shutting down and storing a fuel cell system, particularly for below freezing temperature conditions. The methods comprise stopping power production from the fuel cell stack, monitoring its temperature, and repeatedly performing a predetermined warming operation if the stack temperature falls to a normal threshold temperature. In the improved methods, either an initial threshold temperature and/or an initial warming operation are used that differ from the respective normal threshold temperature and the predetermined warming operation.

Abstract: Improved methods are disclosed for shutting down and storing a fuel cell system, particularly for below freezing temperature conditions. The methods comprise stopping power production from the fuel cell stack, monitoring the amount of energy remaining in an energy supply, monitoring the stack temperature, and repeatedly performing a predetermined warming operation if the stack temperature falls to a normal threshold temperature and if the amount of energy remaining exceeds a certain minimum amount. In the improved methods, when the amount of remaining energy is less than or equal to the minimum amount, a final warming operation is performed that differs from the predetermined warming operation.

Abstract: A device for separating a fluid having a water and gas portion in a fuel cell system includes a fluid inlet an a fluid outlet with an outlet valve. The separating device includes a first reservoir region for collecting the water portion of the fluid. The first reservoir region includes a first outlet to feed the water portion in the direction of the fluid outlet. The separating device also includes a second reservoir region having a second outlet that feeds the water portion in the direction of the fluid outlet so that the first reservoir region 19 is connected in series in terms of flow via the second reservoir region with the fluid outlet. In an installation position of the separating device the first outlet is arranged lower than the second outlet so that deposits of the water portion completely covering the first outlet are prevented from flowing away.

Abstract: Bipolar plate assemblies are disclosed in which the transition fuel channels are offset from the transition oxidant channels in the transition regions on the active sides of the plates. This configuration allows for a reduced pressure drop in the coolant flow in the transition regions on the inactive, coolant side of the plates and thereby improves coolant flow sharing. The assemblies are suitable for use in high power density solid polymer electrolyte fuel cell stacks.

Abstract: Improved methods are disclosed for shutting down and storing a fuel cell system, particularly for below freezing temperature conditions. The methods comprise stopping power production from the fuel cell stack, monitoring the amount of energy remaining in an energy supply, monitoring the stack temperature, and repeatedly performing a predetermined warming operation if the stack temperature falls to a normal threshold temperature and if the amount of energy remaining exceeds a certain minimum amount. In the improved methods, when the amount of remaining energy is less than or equal to the minimum amount, a final warming operation is performed that differs from the predetermined warming operation.

Abstract: A system and method is provided for minimizing the degradation of a fuel cell after shutdown by forcing remaining air out of a fuel cell system. Upon fuel cell shutdown, the flow of air to the cathode of the fuel cell can be kept at a low rate. The flow of cathode exhaust gases along an exhaust conduit is substantially restricted while the pressure of the supply air supplied is increased. As a result, the pressure of the cathode exhaust gases in the exhaust conduit increases. The voltage of the fuel cell can be to deplete the oxygen in the supply air. The pressure of the supply air is decreased to a pressure lower than the pressure of the cathode exhaust gas in the exhaust conduit such that the cathode exhaust gas flows backward through the system to push out any remaining air.

Abstract: Methods are disclosed for starting up a fuel cell system from subzero temperatures using the latent heat of crystallization available in a water supply maintained at above freezing temperature. During start-up, a water spray subsystem is used to spray water from the supply onto a heat exchange surface in a heat exchange element through which coolant from a fuel cell stack coolant circuit is circulating. The water freezes onto the heat exchange surface and the heat of crystallization is exchanged with the circulating coolant across the heat exchange surface, thus warming the coolant.

Abstract: Ruthenium or a Ruthenium compound is applied to an anode structure according to a predetermined pattern, with only part of the anode active area containing Ru. The parts of the MEA that do not contain Ru are not expected to suffer degradation from Ru cross-over, so that overall degradation of the cell will be diminished. Having less precious metals will also translate into less cost.

Abstract: The pressure drop associated with the coolant flow in the coolant transition regions of a typical high power density, solid polymer electrolyte fuel cell stack can be significant. This pressure drop can be reduced by enlarging the height of the coolant ducts in this region of the associated flow field plate so that the ducts extend beyond the plane of the plate. The height change can be accommodated by offsetting the ducts in adjacent cells in the stack and by employing non planar MEAs in this region. By reducing the pressure drop, improved coolant flow sharing is obtained.

Abstract: Bipolar plate assemblies are disclosed in which the transition fuel channels are offset from the transition oxidant channels in the transition regions on the active sides of the plates. This configuration allows for a reduced pressure drop in the coolant flow in the transition regions on the inactive, coolant side of the plates and thereby improves coolant flow sharing. The assemblies are suitable for use in high power density solid polymer electrolyte fuel cell stacks.

Abstract: A device for separating a fluid having a water and gas portion in a fuel cell system includes a fluid inlet an a fluid outlet with an outlet valve. The separating device includes a first reservoir region for collecting the water portion of the fluid. The first reservoir region includes a first outlet to feed the water portion in the direction of the fluid outlet. The separating device also includes a second reservoir region having a second outlet that feeds the water portion in the direction of the fluid outlet so that the first reservoir region 19 is connected in series in terms of flow via the second reservoir region with the fluid outlet. In an installation position of the separating device the first outlet is arranged lower than the second outlet so that deposits of the water portion completely covering the first outlet are prevented from flowing away.

Abstract: A system and method is provided for minimizing the degradation of a fuel cell after shutdown by forcing remaining air out of a fuel cell system. Upon fuel cell shutdown, the flow of air to the cathode of the fuel cell can be kept at a low rate. The flow of cathode exhaust gases along an exhaust conduit is substantially restricted while the pressure of the supply air supplied is increased. As a result, the pressure of the cathode exhaust gases in the exhaust conduit increases. The voltage of the fuel cell can be to deplete the oxygen in the supply air. The pressure of the supply air is decreased to a pressure lower than the pressure of the cathode exhaust gas in the exhaust conduit such that the cathode exhaust gas flows backward through the system to push out any remaining air.

Abstract: To reduce degradation of a solid polymer fuel cell during startup and shutdown, a selectively conducting component is incorporated in electrical series with the anode components in the fuel cell. The component is characterized by a low electrical resistance in the presence of hydrogen or fuel and a high resistance in the presence of air. High cathode potentials can be prevented by integrating such a component into the fuel cell. A suitable selectively conducting component can comprise a layer of selectively conducting material, such as a metal oxide.